[compiler-rt] r290861 - [XRay] [compiler-rt] Include argv[0] in the log file name.

[Dean Michael Berris via llvm-commits]

Author: dberris
Date: Mon Jan  2 22:35:24 2017
New Revision: 290861

URL: http://llvm.org/viewvc/llvm-project?rev=290861&view=rev
Log:
[XRay] [compiler-rt] Include argv[0] in the log file name.

Summary:
If you decide to recompile parts of your Linux distro with XRay, it may
be useful to know which trace belongs to which binary.  While there, get
rid of the incorrect strncat() usage; it always returns a pointer to the
start which makes that if() always true.  Replace with snprintf which is
bounded so that enough from both strings fits nicely.

Reviewers: dberris

Subscribers: danalbert, srhines, kubabrecka, mgorny, llvm-commits

Differential Revision: https://reviews.llvm.org/D27912

Added:
    compiler-rt/trunk/test/xray/TestCases/Linux/argv0-log-file-name.cc
Modified:
    compiler-rt/trunk/lib/xray/xray_inmemory_log.cc

Modified: compiler-rt/trunk/lib/xray/xray_inmemory_log.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/xray/xray_inmemory_log.cc?rev=290861&r1=290860&r2=290861&view=diff
==============================================================================
--- compiler-rt/trunk/lib/xray/xray_inmemory_log.cc (original)
+++ compiler-rt/trunk/lib/xray/xray_inmemory_log.cc Mon Jan  2 22:35:24 2017
@@ -112,14 +112,23 @@ static int __xray_OpenLogFile() XRAY_NEV
   // Open a temporary file once for the log.
   static char TmpFilename[256] = {};
   static char TmpWildcardPattern[] = "XXXXXX";
-  auto E = internal_strncat(TmpFilename, flags()->xray_logfile_base,
-                            sizeof(TmpFilename) - 10);
-  if (static_cast<size_t>((E + 6) - TmpFilename) > (sizeof(TmpFilename) - 1)) {
-    Report("XRay log file base too long: %s\n", flags()->xray_logfile_base);
+  auto Argv = GetArgv();
+  const char *Progname = Argv[0] == nullptr ? "(unknown)" : Argv[0];
+  const char *LastSlash = internal_strrchr(Progname, '/');
+
+  if (LastSlash != nullptr)
+    Progname = LastSlash + 1;
+
+  const int HalfLength = sizeof(TmpFilename) / 2 - sizeof(TmpWildcardPattern);
+  int NeededLength = internal_snprintf(TmpFilename, sizeof(TmpFilename),
+                                       "%.*s%.*s.%s",
+                                       HalfLength, flags()->xray_logfile_base,
+                                       HalfLength, Progname,
+                                       TmpWildcardPattern);
+  if (NeededLength > int(sizeof(TmpFilename))) {
+    Report("XRay log file name too long (%d): %s\n", NeededLength, TmpFilename);
     return -1;
   }
-  internal_strncat(TmpFilename, TmpWildcardPattern,
-                   sizeof(TmpWildcardPattern) - 1);
   int Fd = mkstemp(TmpFilename);
   if (Fd == -1) {
     Report("XRay: Failed opening temporary file '%s'; not logging events.\n",

Added: compiler-rt/trunk/test/xray/TestCases/Linux/argv0-log-file-name.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/test/xray/TestCases/Linux/argv0-log-file-name.cc?rev=290861&view=auto
==============================================================================
--- compiler-rt/trunk/test/xray/TestCases/Linux/argv0-log-file-name.cc (added)
+++ compiler-rt/trunk/test/xray/TestCases/Linux/argv0-log-file-name.cc Mon Jan  2 22:35:24 2017
@@ -0,0 +1,14 @@
+// Check to make sure argv[0] is contained within the (randomised) XRay log file
+// name.
+
+// RUN: %clangxx_xray -std=c++11 %s -o %t
+// RUN: %run %t > xray.log.file.name 2>&1
+// RUN: ls | FileCheck xray.log.file.name
+// RUN: rm xray-log.* xray.log.file.name
+
+#include <cstdio>
+#include <libgen.h>
+
+[[clang::xray_always_instrument]] int main(int argc, char *argv[]) {
+  printf("// CHECK: xray-log.%s.{{.*}}\n", basename(argv[0]));
+}